In systems for the control of fixed wing aircraft or helicopter engines, it has previously been proposed to use pressure responsive systems including pressure sensors of the electromechanical types. However, these prior systems have been relatively expensive, and in some cases have been subject to failure or to a lack of reliability. Further, this type of pressure transducer tends to have more uncontrolled component hysteresis than might be desirable, and is subject to variations with extremes of temperature often found in aircraft environments, and the output may be adversely affected by humidity or other ambient conditions. Particularly where the transducer is intended to measure adverse operating conditions in or near a jet or turbine engine, it is important that the pressure transducer which is employed be highly stable under adverse conditions. In addition, where switching circuits are used, it is important to insure positive operation of the circuitry.
Accordingly, an important object of the present invention is to improve the reliability of aircraft engine control systems involving the sensing of pressure.